Chrome iron ore (x) was heated with dry `Na_(2)CO_(3)` in the presence of quick lime and air in a furnace. The mixture was extracted with water and filtered. The filtrate was yellow(A) which on adding conc. `H_(2)SO_(4)` turned to orange red. The solution was evaporated and cooled. The crystals of B were obtained. To the crystals in aqueous solution, `NH_(4)Cl` was added. On fractional crystallization, orange red crystals (C ) is formed.
B was obtained by fractional crystallization. The compound crystallized first was
A. `Na_(2)Cr_(2)O_(7).2H_(2)O`
B. `NaCl`
C. `Na_(2)CO_(3)`
D. `Na_(2)SO_(4).10H_(2)O`